Russian poison plot police coming to UK

Russian detectives are to be allowed unprecedented access to exiled oligarchs living in Britain as part of the investigation into the poisoning of former KGB agent Alexander Litvinenko.

The Observer has learnt that the Home Secretary, John Reid, has signed a commission rogatoire, a legal instrument permitting co-operation between foreign countries, that will allow the Russian authorities to dispatch investigators to the UK.

The decision will allow Russia to interview leading critics of President Putin living in Britain - long the target of Russian extradition efforts - in connection with the Litvinenko murder. Kremlin investigators, in an investigation parallelling Britain's, have drawn up a list of dozens of suspects including wealthy anti-Putin exiles.

Among the names reported to be high on the Kremlin list is Boris Berezovsky, the former media and oil tycoon, who was a close friend of Litvinenko. Berezovsky has accused the Russian authorities of being behind Litvinenko's death, a claim which the Kremlin has indignantly denied.

He built up an estimated £800m fortune during Russia's privatisation programme and fled to the UK six years ago. Moscow tried to extradite him, initially on fraud charges, and subsequently on the grounds that he was plotting to overthrow the Russian government. But Britain, convinced that he faced the risk of political victimisation back home, granted him political asylum. This, his lawyers have contended, will make it impossible for Russia to win his extradition on what they term trumped-up charges in connection with the Litvinenko case.

With British police eager to return to Russia to continue their own inquiries, confirmation of the agreement to allow the Russians to come to the UK will raise questions about whether there has been a trade-off.

Anti-Putin dissidents are also keen to establish whether the visiting Russian detectives will be subject to constraints similar to those imposed on their British investigators when they visited Moscow last year. The British were allowed only to observe suspects and witnesses being questioned by Russian prosecutors. Last Friday, the newspaper Moskovsky Komsomolets reported that the Home Office had twice sent back a request from Russian prosecutors asking to visit Britain, citing 'irregularities' and 'minor insufficiencies and non-observance of inter-state [legal] agreements'.

A spokesman for Russia's prosecutor general declined to comment yesterday. But sources in Moscow said the difficulties had been overcome, paving the way for Russian detectives to visit Britain.

Russia's deputy prosecutor-general, Alexander Zvyagintsev, has said his team wants to question more than 100 witnesses and visit dozens of sites. Russian officials have also said the investigators want to speak to Chechen rebel envoy Akhmed Zakayev, an ally of Litvinenko and another strident critic of Putin.

Last week the Metropolitan Police handed its file on the investigation into Litvinenko's murder to the Crown Prosecution Service. It has been reported that the British government is preparing to demand the extradition of a Russian businessman, Andrei Lugovoi, to stand trial for Litvinenko's fatal poisoning. Lugovoi, a former KGB officer, was interviewed by detectives from Scotland Yard's counter-terrorism unit in Moscow late last year.

He met Litvinenko several times - including one encounter at the Millennium Hotel, Grosvenor Square, London, on 1 November. Litvinenko fell ill shortly afterwards and died on 23 November. Traces of radioactive polonium-210 were found at a number of offices and hotels around London visited by Lugovoi and in a plane in which he travelled.

Lugovoi has protested his innocence and said he has been interviewed by police only as a witness.

A spokesman for Berezovsky said that the oligarch was prepared to meet Russian investigators. 'If the British police want him to co-operate, he has said he will do so,' the spokesman said. 'This is providing that he has his lawyers with him and the Russians are searched beforehand.'